The present invention relates to fluid-operated disengaging apparatus for clutches, especially for clutches which are used in automotive vehicles. More particularly, the invention relates to improvements in clutch disengaging apparatus of the type disclosed, for example, in German Offenlegungsschrift No. 2,217,943.
The disengaging apparatus which is disclosed in the German publication employs a housing defining an annular cylinder chamber which is open at one end and receives an annular piston for a throw-out bearing. The apparatus further employs a membrane whose inner and outer marginal portions are secured to the housing, which has a median portion contacting the piston, and which further comprises an outer corrugation adapted to roll in an outer annular clearance between the cylinder and the external surface of the piston as well as an inner corrugation which can roll in an inner annular clearance between the internal surface of the piston and an adjacent housing wall when the piston moves axially of the cylinder chamber. The piston has freedom of radial movement with reference to the housing, i.e., the width of the inner and/or outer annular clearance can change in dependency on the extent of radial movement of the piston. The only means for guiding the piston are the aforediscussed corrugations of the membrane whose guiding or centering action is weak or negligible. If the piston is not in exact register with the rotary parts of the clutch, for example, with the customary diaphragm spring which is normally used in a friction clutch to establish or terminate the torque transmitting connection between the driving and driven components of the clutch, the corrugations of the membrane as well as other parts of the disengaging apparatus and/or clutch are subjected to pronounced stresses and wear which can result in shorter useful life of such parts and can entail considerable expenses for frequent inspection and maintenance.